The aircraft departed from Parafield with three persons on board. The pilot estimated the aircraft weight was within tolerance, being just below the allowable maximum all up weight for the aircraft type. The destination airstrip had a steep uphill gradient in the landing direction to the north. A 20 kt to 30 kt northerly wind was blowing at the time. The pilot assessed the situation, but because the wind was not generating a great deal of turbulence he believed it to be lighter, but he still decided to make a shallow approach at a slightly faster speed. On final approach, as the aircraft descended through about 500 ft above ground level (AGL), the pilot believed it experienced windshear, with the airspeed decreasing from 70 kt to 60 kt, and an increase in the rate of descent. On short final the pilot reduced power, then flared for the landing but too high. He felt the aircraft sink but did not increase power to arrest the descent, with the result the aircraft struck the ground heavily on its main wheels, bounced, then turned to the left impacting the ground again with the left main wheel, left wingtip, nose wheel, and propeller. The nose gear separated, and the left main gear fractured. A witness on the ground reported that a stronger wind gust occurred just as the aircraft was on short final and commencing to flare at about 20 ft AGL. It then sank rapidly to the ground. The pilot probably misjudged the flare height due to the steep incline of the airstrip, allowed the airspeed to decay, then failed to apply power to prevent the subsequent high sink rate. The heavy aircraft weight, and the wind roll over effect in the lee of the hill, would have contributed to the rapid rate of descent.